thanks for the clarification, Gary. So I would like to restate my
question as follows: do you know of any (atempts at) implementations of
a sandbox based on closures? It seems to me that there are some tricky
issues like how the permissions get into the closure or how privileged
code is called. But that's probably due to the limitations on my
imagination.
Meanwhile, at Artima
(http://www.artima.com/weblogs/viewpost.jsp?thread=161019) and
ObjectMentor
(http://blogs.objectmentor.com/ArticleS.MichaelFeathers.ItsTimeToDeprecateFinal),
people are also discussing the 'final kludge', calling for 'final' to
become deprecated. It would be nice to think there is something that
could take its place :-)
kr,
Yo
Gary McGraw wrote:
You guys are both right, but talking about different things.
You can kludge pretend closure for a security critical section using the static
final nonsense to make a hole on the unbound environment. I described this in
some detail in a 1999 javaworld article. Havung closure would lead to a better
sandbox.
The luring attacks that john describes were not what I was getting at, but they
lend more weight to the argument for closure.
Yay, language arcana!
gem
-----Original Message-----
From: Johan Peeters [mailto:[EMAIL PROTECTED]
Sent: Sun May 21 09:08:14 2006
To: John Steven
Cc: Gary McGraw; Mailing List, Secure Coding; SSG
Subject: Re: [SC-L] Ajax one panel
We may be at cross purposes. I understand your concern about luring
attacks, John. I am sure you are right and they are feasible, but I
interpreted Gary's comment as meaning 'closures can be used to build a
more reliable sandbox'. But maybe this is not what is meant?
kr,
Yo
John Steven wrote:
Johan,
Yes, the attacks are feasible. Please refer to the Java language spec.
on inner/outer class semantics and fool around with simple test cases
(and javap -c) to show yourself what's happening during the compile step.
Attacks require getting code inside the victim VM but mine pass
verification silently (even with verifier turned on). Calling the
privileged class to lure it into doing your bidding requires only an
open package (not signed and sealed -- again see spec.) and other fun-
and-excitement can be had if the Developer hasn't been careful enough
to define the PriviledgedAction subclass as an explicit top-level class
and they've passed information to-and-fro using the inner class
syntactic sugar--rather than explicit method calls defined pre- compile
time.
----
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Technical Director; Principal, Software Security Group
Direct: (703) 404-5726 Cell: (703) 727-4034
Key fingerprint = 4772 F7F3 1019 4668 62AD 94B0 AE7F
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Software Confidence. Achieved.
On May 21, 2006, at 8:23 AM, Johan Peeters wrote:
That sounds like a very exciting idea, but I am not sure about the
mechanics of getting that to work. I assume the permissions for the
untrusted code would be in the closure's environment. Who would put
them there? How would the untrusted code call privileged code?
Has anyone done this?
kr,
Yo
Gary McGraw wrote:
Hi yo!
Closure is very helpful when doing things like crossing trust
boundaries. If you look at the craziness involved in properly
invoking the doprivilege() stuff in java2, the need for closure is
strikingly obvious.
However, closure itself is not as important as type safety is. So
the fact that javascript may (or may not) have closure fails in
comparison to the fact that it is not type safe.
Ajax is a disaster from a security perspective.
gem
-----Original Message-----
From: Johan Peeters [mailto:[EMAIL PROTECTED]
Sent: Sat May 20 15:44:46 2006
To: Gary McGraw
Cc: Mailing List, Secure Coding; SSG
Subject: Re: [SC-L] Ajax one panel
I think Java would have been a better language with closures, but I
am intrigued that you raise them here. Do you think closures present
security benefits? Or is this a veiled reference to Ajax? I guess
JavaScript has closures.
kr,
Yo
Gary McGraw wrote:
Ok...it was java one. But it seemed like ajax one on the show
floor. I participated in a panel yesterday with superstar bill
joy. I had a chance to talk to bill for a while after the gig and
asked him why java did not have closure. Bill said he was on a
committee of five, and got out-voted 2 to 3 on that one (and some
other stuff too). You know the other pro vote had to be guy
steele. Most interesting. Tyranny of the majority even in java.
Btw, bill also said they tried twice to build an OS on java and
failed both times. We both agree that a type safe OS will happen
one day.
Here's a blog entry from john waters that describes the panel from
his point of view.
http://www.adtmag.com/blogs/blog.aspx?a=18564
gem
www.cigital.com
www.swsec.com
Sent from my treo.
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